Method of making resilient batt

ABSTRACT

Batt style insulation comprised of cellulosic and thermoplastic material and a method of making such insulation. A blend of cellulosic material and thermoplastic fibrous material, wherein the latter comprises between 3%-15% of the blend by weight, is formed by a method such as air-laying into a low density, high loft mat. The surface of the mat is flame-treated to melt the thermoplastic component on the surface, forming a skin which keeps the cellulosic component intact. The thermoplastic component in the interior of the mat remains unmelted, thereby providing the mat with a spring-back characteristic which allows the mat to retain most of its original shape and loft even after it has been compressed for shipping. A facing sheet can be applied to the surface of the mat, as is done with conventional fiberglass batt-style insulation.

This is a division of application 08/155,253 filed Nov. 22, 1993 nowU.S. Pat. No. 5,418,031.

BACKGROUND OF THE INVENTION

The present invention pertains generally to the field of thermalinsulation material, and more particularly to the field of thermalinsulation having a cellulosic component.

The use of cellulosic particulates as thermally insulating material incontemporary construction is well-known. Such insulation takes the formof a free-flowing mixture of small cellulosic particles (about 1-10 mmin diameter) and short cellulosic fibers (about 0.5-3 mm in length),such as that shown in U.S. Pat. No. 4,579,592, wherein the particulatestake the form of a low-density collection of cellulosic fibers andcellulosic particles (small chips or splinters). The insulation valuearises from cells of trapped air interspersed between the cellulosicparticulates; such cells are poor conductors of heat, and are of such asize that convective heat transfer is minimal. The cellulosic insulationis applied either wet or dry to the surface or cavity to be insulated.Smaller areas, such as residential attics, may be insulated by simplypouring the insulation onto the surface to be insulated. Larger areasare often insulated by using special equipment which blows theinsulation onto a surface or into a cavity. The mixture may be wettenedwith an adhesive, allowing the mixture to stick to walls, ceilings, andother such surfaces where the dry mixture alone would not remain on thesurface after application.

Cellulosic thermal insulation has several advantages over syntheticinsulation materials. It may be made by processing cellulosic materialsof either virgin or waste origin by shredding, hammer-milling, orotherwise processing them into a fibrous form. It is biodegradable andits manufacture does not involve the emission of environmentally harmfulmaterials, as the manufacture of synthetic insulation materials oftendoes; the manufacture of fiberglass insulation, for example, generallyhas the side effect of emitting formaldehyde into the environment. Thecellulosic insulation may be rendered flame and / or vermin resistant bytreatment with boric acid, mono- and diammonium phosphate, ammoniumsulfate, zinc chloride, sodium tetraborate, or other appropriatesubstances.

However, free-flowing cellulosic insulation has several disadvantages.First, the most common method of application, blowing, requires specialequipment. Second, when used in conjunction with adhesives forapplication to non-horizontal surfaces, application can be messy,time-consuming, and difficult. Third, removal of the mixture isdifficult because of the granular (or, if used with an adhesive,foamlike) form of the fibrous mixture, requiring raking, vacuuming, orscraping for removal. All of these disadvantages can be avoided by useof a batt-style thermal insulator, one which may be affixed to thesurfaces to be insulated by stapling, nailing, or otherwise attaching itto the surface. Such an insulator may be quickly applied without the useof any special equipment, and it may be quickly peeled away for easyremoval or replacement. A batt-style cellulosic insulator wouldtherefore hold several advantages over free-flowing cellulosicinsulation that would make the use of cellulosic insulation moreattractive when compared to synthetic materials.

As used in the specification and claims, "batt-style," "batt," or"batting" refers to a blanket-like product composed of loosely layered,non-woven material, as exemplified by fiberglass batt insulation.

Unfortunately, since the individual particulates of cellulosicinsulation do not adhere to each other well, a method of forming theminto an effective and sturdy batt has heretofore been unknown.

Cotton batts heretofore have been used as sound insulation ("cottonshoddy") underneath carpeting in automobiles and as pipe insulation, butsuch batts are not effective or sturdy enough for heat insulation incontemporary construction. These batts may have densities of about 200kg/cubic meter which is too dense to provide effective heat insulationor adequate physical flexibility for contemporary construction.

The difficulty lies in finding a way to make the cellulosic particulatesbind in such a way that the resulting batt is durable, but yet has theflexibility necessary for it to be folded or rolled for easy packagingand transportation. Further, the particulates must bind in such a waythat the air cells interspersed between the fibers are preserved, if theinsulation value of the cellulosic particulates is to be maintained. Ifthe insulation cannot return to its low-density "fluffy" form, withcells of air interspersed between the insulation particulates, theinsulating properties are largely lost.

One method of binding cellulosic particulates that is disclosed in theprior art is to mix the cellulosic particulates with thermoplasticparticles and apply heat. The thermoplastic component then melts andencapsulates the cellulosic component, whose individual particulatesthen adhere to each other. Examples of such methods are disclosed inU.S. Pat. Nos. 5,082,605, 5,088,910 and 5,096,046. However, this methodproduces a product too rigid for easy packaging and transportation, andfurther does not preserve the insulative value of the cellulosic fibersdue to the resulting high density of the product. Similar drawbacksarise from the use of an adhesive to bind the cellulosic fibers.

While the prior art reveals methods of binding cellulosic particulatesto a flexible substrate material by the use of an adhesive, e.g. U.S.Pat. No. 4,634,621, such a method is not well-suited for the form ofcellulosic particulates used for insulation; such particulates tend tobecome rigid and inflexible when an adhesive is applied.

Fiber reinforced composites have been manufactured utilizing either asingle fiber type or a mixture of fibers to form a nonwoven air-laidbatt which either includes thermoplastic fibers or is resinated with athermoplastic material. This batt is then molded into a preform andmaybe injected with resin (e.g. U.S. Pat. Nos. 4,663,225 and 4,812,283).

SUMMARY OF THE INVENTION

The present invention is directed to a batt-style thermal insulator,made of a combination of cellulosic particulates and thermoplasticfibers, which is durable and may be easily transported, applied, andremoved while still retaining the advantages of free-flowing cellulosicinsulation. The cellulosic particulates ordinarily are composed ofcellulosic particles (about 1-10 mm in diameter) and short cellulosicfibers (about 0.5-3 mm in length). Such material typically is producedby comminuting recycled paper thereby resulting in approximately a 50/50mixture (by weight) of particles and fibers.

The addition of a thermoplastic component to cellulosic insulationimparts a flexible, elastic characteristic to the insulation, allowing abatt made of these materials to spring back to near its original shapeafter it has been subjected to and released from an external force. Inother words, the batt may be rolled up and confined in rolled-up form,but readily may return to its original shape upon removal of suchconfinement. This spring-back characteristic allows the batt to becompressed for shipping without fear that the compression willirreversibly flatten the batt and strip it of its insulating quality.

The thermoplastic fibers provide a matrix for the cellulosicparticulates to allow the mixture to cohere to a greater extent thanwould cellulosic particulates alone, because the thermoplastic fibersentangle the cellulosic particulates as well as each other. Without thethermoplastic fiber matrix, the individual cellulosic particulates wouldfall apart.

The batt may be made more durable by heat treating the batt surface,which melts the thermoplastic component and forms a flexible "skin"which further holds the batt intact and lends it greater durability.Other than this heat treatment, the thermoplastic fibers in the batt ofthe present invention are not joined to one another except byentanglement.

The invention therefore retains the beneficial insulating properties andenvironmental advantages of cellulosic insulation while avoiding theneed for special equipment for its transport, application, and removal.

The present invention involves a batt-style thermal insulator made of amixture of cellulosic particulates and thermoplastic material. Thecellulosic particulates may be prepared from any of the materialscommonly employed to make cellulosic insulation, by any of the methodscommonly employed to make it; the particulates used in the preferredembodiment are made from hammer-milled newspaper. The thermoplasticmaterial may be polyethylene, polypropylene, vinyon, or other plastics,the only limitation being that thermoplastics with a melting temperatureabove 400 F. are not recommended if the batt is to be heat treatedbecause the cellulosic particulates begin to decompose above thistemperature. The preferred embodiment uses thermoplastic fibers made oflow density polyethylene (LDPE), the material which presently forms mostmodern-day plastic film (e.g. garbage bags and peel-off container lids).

To form the invention, thermoplastic fibers of 1-6 denier which are 2-15centimeters in length are mixed with cellulosic insulation material sothat the thermoplastic component forms approximately 3%-15% of themixture by weight. Mixtures within this range have been tested withpositive results. Rather than using solid thermoplastic fibers,specially manufactured hollow thermoplastic fibers may be used in orderto increase the insulating properties of the finished invention. Themixture then is formed into a low density batt (about 10-40 kg/cubicmeter) of high loft by a method such as air-laying, the method used inthe preferred embodiment. Examples of air-laying are given in U.S. Pat.Nos. 3,895,088 and 3,963,391.

While the resulting batt is more durable than any similar batt thatcould be made of cellulosic material alone due to the entanglementcaused by the thermoplastic fibers, such a batt is still not as strongas a synthetic insulating batt and cannot withstand extensive handling.The batt can be made more durable by applying heat to the outer surfacesof the batt, melting the thermoplastic fiber on the surfaces and forminga porous "skin" on the surfaces which imparts greater strength to thebatt. Strength is also imparted due to the action of thermoplasticfibers which happen to extend from one surface to the other; these formcolumns which are bonded to the skins and that hold the skins together.These same fibers also help to impart the spring-back characteristic tothe batt that pushes the skins apart. The invention as described hasbeen heat-treated by passing the batt under an electric heater so thatthe surfaces and edges of the batt reach approximately 350 F. Heattreatment may also be achieved by rolling the batt through calendarrolls containing internal resistance heaters, but this method compressesthe batt during heating and therefore produces a batt with less loft andless insulation value.

The skin renders transportation and installation of the insulation fareasier than they would be for ordinary cellulosic insulation. The skininsures that all of the cellulosic particulates remain within the battduring subsequent handling, whereas a non-heat-treated, "skinless" battwould lose some of its cellulosic component. The batt may be rolled intobundles, as is done for fiberglass batt insulation. The elasticproperties of the unmelted thermoplastic within the interior of the battact as a spring, returning the batt to near its original shape evenafter it has been compressed during the shipping process. The batt maybe stapled or otherwise affixed to the surface to be insulated.

Batt-style insulation often includes some kind of facing sheet over oneor more of its surfaces, and the insulating batt herein disclosed mayuse a facing sheet as well. The facing sheet's ends may extend beyondthe surface of the insulation so that the facing sheet may be nailed orstapled to a surface, rather than driving the fasteners through thebatt, thereby allowing the use of shorter fasteners and promoting easierinstallation. The facing sheet may also be used to modify the insulating(or other) properties of the batt. One common facing sheet forbatt-style insulation is kraft paper affixed to the batt by asphaltspray; the asphalt spray hinders moisture travel through the insulationand serves as a vapor barrier. Another common facing sheet is thin foil,which reduces radiative heat transfer from the surface of theinsulation. Any of these features are attractive possibilities for usein combination with the batt herein disclosed.

The invention may be rendered fire-resistant either by using treatedfibers as the raw ingredients for the batt, or by using untreated fibersand treating the finished batt. Similar steps can be taken to render theinvention vermin-resistant.

Further objects, features, and advantages of the invention will beapparent from the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an embodiment of an apparatus for making theinsulation.

FIG. 1A is a view of the loading and mixing stage of the apparatus formaking the insulation.

FIG. 1B is a view of the metering and processing stage of the apparatusfor making the insulation.

FIG. 1C is a view of the batt-making and heating stage of the apparatusfor making the insulation.

FIG. 2 is a view of an alternate means of heat treatment of the batt,involving the use of heated calendar rolls.

FIG. 3 is a view of the insulating batt before heat treatment.

FIG. 4 is a view of the insulating batt after heat treatment.

DETAILED DESCRIPTION OF THE INVENTION

An apparatus for making the insulation is shown in its entirety inFIG. 1. The components of the apparatus of FIG. 1 are divided into threeparts, each of which is shown in FIGS. 1A, 1B, and 1C.

FIG. 1A shows hopper 10, containing cellulosic particulates 12, andhopper 14, containing thermoplastic fibers 16. The cellulosicparticulates 12 are made of hammer-milled newspaper. The thermoplasticfibers 16 are low density polyethylene (LDPE) fibers of 1-6 denier and2-15 centimeters in length. Both types of fiber may tangle into clumps,so some means of de-clumping the fibers may be necessary at a laterstage of processing. The hoppers 10 and 14 have a metering mechanismwhich only releases 3%-15% thermoplastic fibers for every unit of weightof cellulosic particulate released, thereby insuring a proper componentratio for the finished batt. While an insulating batt with less than 3%or greater than 15% thermoplastic component by weight is likelypossible, such an insulating batt has not yet been produced and tested.

The cellulosic particulates 12 and thermoplastic fibers 16 are carriedunmixed by conveyor 18 into a mixing chamber 20. Here a fan 22 producesa high-speed swirl of air within the chamber which thoroughly mixes thecellulosic particulates 12 and thermoplastic fibers 16. The mixedcomponents 24 are blown by the fan 22 out of the mixing chamber 20 intoa closed duct 26, which carries the mixture 24 to the next stage inprocessing, shown in FIG. 1B.

FIG. 1B shows the closed duct 26 transferring the mixture 24 to conveyor30, which in turn transfers the mixture 24 to conveyor 32. The belt ofconveyor 32 has scoops 34 to assist the conveyor 32 in carrying themixture 24 up its incline. At the top of the incline lies the meteringpassage 36, where part of the mixture 24 is skimmed off to insure that auniform flow of the mixture 24 enters the next stage of processing. Themetering wheel 38 has scoops 40 which have very little clearance overthe scoops 34 on the conveyor 32, so any amount of mixture 24 extendingover the top of the scoops 34 will be taken off by the scoops 40. Afterthe metered mixture 44 leaves the metering passage 36, it is pulled bythe conveyors 42 into the next stage of processing, shown in FIG. 1C.

FIG. 1C shows the final stage of processing. The conveyors 42 pull themetered mixture 44 into the lickerin 50, whose sharp teeth pull apartany clumps of fiber that the metered mixture 44 may have formed; thede-clumped mixture is shown at 52. The lickerin 50 throws the de-clumpedmixture 52 into an air-laying apparatus so that the fibers may be formedinto a batt. The air-laying apparatus basically consists of a rotatingperforated drum 54 and a fan 56. The fan 56 pulls air away from thelickerin 50 and through the perforated drum 54 by way of an air passage58, pulling the de-clumped mixture 52 tightly against the perforateddrum 54. The fibers thereby lay over each other and tangle, forming abatt 60. After the perforated drum 54 rotates the batt 60 so that it nolonger lays over air passage 58, the batt 60 is no longer being pulledonto the perforated drum 54, allowing its separation from the perforateddrum 54 by the wedge 62. The batt 60 is then guided out of theair-laying apparatus by rollers 64, and it is shown in its finishedstate at 66. The batt 66 may then be heat-treated if desired; aheat-treated batt has durability superior to a batt which is not heattreated.

If the batt is to be heat-treated, the rollers 64 guide the batt 66 intothe heating chamber 68. The heating chamber 68 contains electricalheating elements 70 which maintain the interior of the heating chamber68 at approximately 350 F. An open-flame method of heating, such asexposed burning gas jets, is also acceptable. The size of the heatingchamber 68 and the speed of the batt's passage must be such that thethermoplastic fibers at the surface of the batt 66 have time to melt andform a skin. If the batt 66 is subjected to heat for too long, thefibers on the interior of the batt 66 will melt, decreasing its loft andhence its insulating value. The heat-treated batt, in essentially itsfinished form, emerges with a skin at 72 as it is pulled from theheating chamber 68 by take-up rollers 74. A sprayer 76 may then spraythe batt 72 with a coat of asphalt over one of the batt's faces; theasphalt serves as both a vapor barrier and an adhesive. A roll of facingsheet 80 can then be applied to the sticky face of the batt 72 by theroller 82. The final batt, with facing sheet applied, can then be woundinto a roll at 84.

FIG. 2 shows an alternate means of heating the batt to form the skin.The rollers 64 guide the batt 66 into the heating chamber 68, whichcontains calendar rolls 86 whose surfaces are maintained atapproximately 350 F. A skin forms as the batt 66 passes through thecalendar rolls 86, and the batt emerges at 72 as it is pulled from theheating chamber 68 by take-up rollers 74. The disadvantage of the use ofcalendar rolls 86 is that it tends to compress the batt 66 as it isheated, leading to decreased loft (and insulation value) after the batt72 cools.

FIGS. 3 and 4 are views of the height of the batt before and afterheating. FIG. 3 shows the batt 66 before heat treatment; the cellulosicparticulates 12 are dispersed throughout the entangled thermoplasticfibers 16. FIG. 4 shows the batt 72 after heat-treatment. Thethermoplastic fibers 16 at the surface of the batt 72 have melted andfused, forming the skin 90. Some of the thermoplastic fibers 16 extendfrom one face of the batt 72 to the other. These fibers make itdifficult for the skin 90 to peel from either face of the batt.

It is understood that the invention is not confined to the particularconstruction and arrangement of parts herein illustrated and described,but embraces such modified forms thereof as come within the scope of thefollowing claims.

What is claimed is:
 1. A method of making a resilient batt suitable foruse as a thermal insulation, the method comprising the steps of:mixingcellulosic particulates and thermoplastic fibers to form a mixture inwhich the cellulosic particulates are entangled by the thermoplasticfibers, wherein the cellulosic particulates include cellulosic particlesand cellulosic fibers, the cellulosic particles being substantially 1-10mm in diameter and the cellulosic fibers being substantially 0.5-3.0 mmin length and wherein the thermoplastic fibers are 3-15% of the mixtureby weight, are 1-6 denier and are 2-15 cm in length; and forming aninsulating batt from the mixture; and heat treating at least one surfaceof the batt to melt the thermoplastic fibers at the at least one surfaceof the batt without melting the thermoplastic fibers in the interior ofthe batt to form a heat treated batt having at least one skin whereinthe thermoplastic fibers in the interior of the heat treated batt areunmelted and are joined to one another only by entanglement and whereinthe batt is capable of being compressed, rolled-up and confined inrolled-up form and returning to its original shape upon removal of theconfinement.
 2. The method of claim 1, wherein at least one of thecellulosic particulates and thermoplastic fibers is fire resistant. 3.The method of claim 1 further including the step of treating the batt sothat the batt is fire resistant.
 4. The method of claim 1, wherein atleast one of-the cellulosic particulates and thermoplastic fibers isvermin resistant.
 5. The method of claim 1 further including the step oftreating the batt so that the batt is vermin-resistant.
 6. The method ofclaim 1, wherein the thermoplastic fibers are hollow.
 7. The method ofclaim 1 further including the step of affixing a facing sheet to theheat treated batt.
 8. The method of claim 7, wherein the facing sheet iskraft paper.
 9. The method of claim 7, wherein the facing sheet ismetallic foil.
 10. The method of claim 7 wherein the step of affixingincludes the steps of spraying an asphalt spray on a surface of saidheat treated batt and placing said facing sheet on said asphalt.
 11. Themethod of claim 1, wherein two surfaces of the batt are heat treated inthe heat treating step and the two surfaces are heat treated usingheated rolls.